Using YUV420 for OpenGL accelerated video playback

I'm reposting this because it seems that the last message was
corrupted...

OK, I'm trying to get 'y420' (i.e kYUV420PixelFormat) data from
QuickTime (via QTNewGWorldFromPTR(...)) and into OpenGL for accelerated
video playback but I'm having more than a few problems along the way.

I'm using ARB_fragment_program to extract the Y, Cb, and Cr planes from
my buffer and then convert them into RGB for display, now I'm pretty
(i.e. ~90%) sure that the fragment program I'm using for this is
correct (I used information gained from Nvidia's HLSL VideoFilter
example) but my input texture seems to be solid black (as shown in
Apple's OpenGL Profiler) so I'm obviously doing something stupid in
my setup code given below. I got the following code from the list
archives and (on the surface) it seems like it should be correct.

Does QuickTime allocate a offscreen pixMap buffer for you when one uses
kYUV420PixelFormat and PlanarPixmapInfoYUV420? I wasn't sure about
this.

In case anyone is wondering why I'm bothering to go through all of this
trouble (i.e. why not just use 'yuvs' w/ Apple's YCBCR_422 texturing
extension) it's because QuickTime has this nasty habit of performing a
scalar (i.e. slow and unoptimized) YUV 4:2:0 to YUV 4:2:2 color-space
conversion before sending the video data to the GPU. With today's
hardware there just isn't any need for this to happen.

Let me also say that there is no documentation (that I could find) on
using QuickTime's 'y420' format for video playback (or otherwise).

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